The former owner of infamous Manhattan club Studio 54 is releasing a tell-all book dishing on the wild cocaine parties and the antics of stars including John Belushi,Robin Williams — and even a “boring” Donald Trump.

Mark Fleischman, who bought the club from original owners Ian Schrager and Steve Rubell and reopened it in the early ’80s, is releasing ­“Inside Studio 54” via Rare Bird on Sept. 19.

Fleischman tells us, “Ian painted a glossy picture of Studio 54, but this is the real story. There were drugs all over the place — that’s what fueled it. I partied with the people who loved cocaine. Belushi used to freebase and would get extremely aggressive with the clientele and staff. Robin ­Williams would get very energetic and funny.”

He said that after Schrager and Rubell were shut down, he had to sign an affidavit promising no more cocaine parties in the basement.

“So I moved the private parties to my office,” said Fleischman.

“You’d see Liza Minnelli, Dodi Fayed, Robin and Dudley Moore there all the time.”

Of Minnelli, “She became a different person. She was overtaken by drugs and alcohol, then she went to Betty Ford.”

Liza Minnelli at Studio 54WireImage

Fleischman also got clean after visiting Mexico’s Rancho La Puerta in 1988, and he now runs gyms.

Back in the day, the party would start at Fleisch­man’s penthouse.

“One day, I was sorting the good coke from the regular coke, and all of a sudden I look up and there’s Lawrence of Arabia standing over me. Peter O’Toole said, ‘May I have some, please?’ Of course I shared the best coke I had with him and he came to Studio 54.”

And Robert De Niro once locked himself in the bathroom with a Jacuzzi full of Champagne.

Trump was another club regular, but “he never touched drink or drugs. He liked looking at beautiful women, even though he was married to Ivana.

Trump wasn’t a lot of fun — when you’re in a crowd drinking and drugging and one person isn’t, that person seems boring.”

Not everyone was in the party spirit: The club was nearly destroyed by Hells Angels in 1984, who threw a busboy off the balcony and “stuffed patrons head-first into garbage pails.”